Ancestral inference.

Abstract

The Tristan da Cunha data for the MN-blood types and for retinitis pigmentosa are analyzed according to the methods for ancestral inference developed previously. Joint and marginal likelihoods for the MN data show that it is possible to make inferences about the types of original founder genes, although relative values are in some cases not large. Although relative likelihoods are robust against small changes in gene frequency, they can be distorted by assuming values that differ widely from the maximum likelihood estimate. A certain ancestral couple was identified as the most likely founders responsible for the introduction of the retinitis pigmentosa allele when an allele frequency of 0.01 was assumed. The inferences for this trait are complicated by the fact that it is recessive, and genotypes are therefore not observable. Extinction probabilities for a variety of sets of originial founder genes on the Tristan da Cunha ancestral pedigree are also computed and discussed.